There have been a number of attempts in the past to provide nursery tray configurations that can be readily indexed through a transplanting mechanism. One such attempt required the total removal of side walls from the tray thereby allowing indexing to be achieved off the edges of the entire row of individual cells in the longitudinal direction of the cell. While this tray has been used, it does suffer from a number of practical problems including a lack of strength caused by the removal of the side walls and the fact that the trays readily nested one into the other causing significant de-stacking problems with automated machinery. Further, the lack of strength caused size limitations and for all the foregoing reasons, this type of tray has not been popular in the nursery industry.
A further attempt to enable convenient tray indexing involved using a side wall rack along the length of the tray wall. This type of tray necessarily meant that the cells around the outer edge of the tray were dissimilar in dimensional size to the other cells. This unfortunately retards growth in the outer cells. Indexing along the length of the tray also significantly decreases the overall longitudinal strength of the tray or reduces the depth of the engaging means causing ineffective indexing.
A still further method of indexing utilised in the past used parallel slots running the entire length of the tray underneath the tray. This arrangement has the effect of overall weakening thus minimising tray strength and breakaway sections at the base cells of the tray can often occur. Nursery trays are commonly treated relatively harshly in use and any weakening of the aforementioned kind results in a greatly lessened useful life for the trays. The breakaway sections of the tray should they occur also can cause an entrapment of roots thus making plant ejection difficult.
A still further proposal for indexing trays of this type suggested in the past is to provide trays with side walls having a plurality of evenly spaced enclosed apertures along their length to provide a basis for engagement with an indexing mechanism. Unfortunately, such trays have required complex indexing mechanisms and moreover, have not readily provided a means for utilising a simple indexing mechanism to index a plurality of adjacently positioned trays in a continuous indexing process.
There are also certain other difficulties that need to be considered when providing a nursery tray configured for a continuous indexing process. The trays themselves are produced from moulded plastics and it has been found that currently available trays (of the same type) can vary up to six mm in longitudinal length. This may be due to thermal expansion, poor die quality or ratios of various plastics and fillers batch to batch, but for whatever reason, such variations make it very difficult to obtain complete engagement and accuracy with the indexing mechanism. Furthermore, with trays of the type including apertures in the side wall, the variation of tray length causes particular problems with indexing mechanism engagement. Other aspects that commonly occur with tray usage is tray corner damage as a result of trays being dropped on their corners in general day to day use. Most currently available trays have a marked lack of reinforcement on the corners and ends of the trays where most impacts occur.
Additionally, in the nursery industry, the main means to support trays has been by the use of a T-Bar mechanism whereby the trays sit on the bottom flange of an inverted T-Bar. This type of structure renders severe root growth problems with at least the end cells of the tray actually sitting on the T-Bar flange. The problem would be worse in any facility where the tray is allowed to sit on a solid or semi-solid surface for any length of time during the growth of seedlings in the tray. It is a common phenomenon for root growth to pass through the open lower end of the cell and form an intertwining mat beneath the cells when there is no clear air space between the cell bottoms and an underlying surface. There may, in such circumstances be little root growth actually within the cell due to the vigour of the plant root growth being expended outside of the cell. This causes problems in ejecting the seedlings from the cells during transplanting and moreover, could result in a seedling being transplanted with little or no root mass as a result of most of the root mass being left below the tray.
In a related aspect, the present invention aims at providing a nursery system that can enable trays to be readily handled during growing phases of seedlings within the tray without causing substantial root growth outside the cell which is controlled by exposure to air (aerial pruning) but which can also be used conveniently in an automatic transplanting mechanism. During seedling growth phases, it might be desired for a nursery to support many nursery trays in a manner whereby they can be moved between various conditions such as full sun, full shade, part shade and perhaps through a watering zone or from the growing area to loading/dispatch zone. As noted above, currently available nursery systems normally support nursery trays on at least flat surfaces along their edges, if not over their full base regions, and are normally moved manually or semi-manually between different areas.
The objective therefore of the present invention is to provide an improved nursery tray and a method of moving or indexing such trays which will meet some or all of the aforementioned difficulties associated with conventional nursery trays. In accordance with a related aspect, the present invention also aims at providing a novel arrangement for handling nursery trays during growth phases for seedlings grown in the trays.